U.S. patent number 11,086,185 [Application Number 16/150,388] was granted by the patent office on 2021-08-10 for light beam direction control element, display device, and manufacturing method for light beam direction control element.
This patent grant is currently assigned to TIANMA JAPAN, LTD.. The grantee listed for this patent is TIANMA JAPAN, LTD.. Invention is credited to Kunihiro Shiota, Ken Sumiyoshi, Takumi Usukura.
United States Patent |
11,086,185 |
Shiota , et al. |
August 10, 2021 |
Light beam direction control element, display device, and
manufacturing method for light beam direction control element
Abstract
A light beam direction control element includes: a first
transparent substrate; a second transparent substrate facing the
first transparent substrate; a first conductive film pattern having
openings and being formed on a surface of the first transparent
substrate opposing the second transparent substrate; a second
conductive film pattern having openings and being formed on a
surface of the second transparent substrate opposing the first
transparent substrate; an electrophoretic element being sandwiched
between the first and second conductive film patterns, and
including light-shielding electrophoretic particles having a
surface charge and a transparent dispersion medium; and
light-transmissive regions being disposed between the first and
second transparent substrates, being sandwiched between at least a
portion of the openings of the first and second conductive film
patterns, having a surface parallel to the first and second
conductive film patterns, and having side walls surrounded by the
electrophoretic element.
Inventors: |
Shiota; Kunihiro (Kawasaki,
JP), Sumiyoshi; Ken (Kawasaki, JP),
Usukura; Takumi (Kawasaki, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
TIANMA JAPAN, LTD. |
Kanagawa |
N/A |
JP |
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Assignee: |
TIANMA JAPAN, LTD. (Kanagawa,
JP)
|
Family
ID: |
65896516 |
Appl.
No.: |
16/150,388 |
Filed: |
October 3, 2018 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20190100853 A1 |
Apr 4, 2019 |
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Foreign Application Priority Data
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Oct 4, 2017 [JP] |
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JP2017-194506 |
Jun 13, 2018 [JP] |
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JP2018-113134 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02F
1/167 (20130101); G02F 1/1681 (20190101); G02B
5/003 (20130101); G02F 1/133524 (20130101); C25D
13/12 (20130101); G02F 1/1323 (20130101); G02B
27/142 (20130101); G02B 2207/123 (20130101) |
Current International
Class: |
C25D
13/12 (20060101); G02B 27/14 (20060101); G02B
5/00 (20060101); G02F 1/167 (20190101); G02F
1/1681 (20190101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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107621722 |
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Jan 2018 |
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CN |
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2015/122083 |
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Aug 2015 |
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WO |
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WO2015/141740 |
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Sep 2015 |
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WO |
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Primary Examiner: King; George G
Attorney, Agent or Firm: Sughrue Mion, PLLC
Claims
What is claimed is:
1. A display device comprising: a light beam direction control
element; and a display unit, wherein the light beam direction
control element comprises: a first transparent substrate; a second
transparent substrate disposed so as to face the first transparent
substrate; a first conductive film pattern that has openings and
that is formed on a first surface of the first transparent
substrate opposing the second transparent substrate; a second
conductive film pattern that has openings and that is formed on a
second surface of the second transparent substrate opposing the
first transparent substrate; an electrophoretic element that is
sandwiched between the first conductive film pattern and the second
conductive film pattern, and that includes light-shielding
electrophoretic particles that have a surface charge and a
transparent dispersion medium; and a plurality of
light-transmissive regions that are disposed between the first
transparent substrate and the second transparent substrate, that
are sandwiched between at least a portion of the openings of the
first conductive film pattern and at least a portion of the
openings of the second conductive film pattern, that have a surface
parallel to the first conductive film pattern and the second
conductive film pattern, and that have side walls surrounded by the
electrophoretic element, wherein the display unit comprises a
display surface that displays an image, wherein the first
conductive film pattern is a conductive light-shielding film
pattern and the second conductive film pattern is a transparent
conductive film pattern, wherein a surface of the second
transparent substrate opposite the second surface is bonded to the
display unit, wherein the first conductive film pattern and the
second conductive pattern are stripe shapes arranged in a
complementary positions to the plurality of the light-transmissive
regions, and wherein a pattern width of the first conductive film
pattern and a pattern width of the second conductive film pattern
are greater than a width of the electrophoretic element.
2. The display device according to claim 1, wherein a pattern width
of one of the first conductive film pattern and the second
conductive film pattern is greater than a pattern width of another
of the first conductive film pattern and the second conductive film
pattern.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This Non-provisional application claims priority under 35 U.S.C.
.sctn. 119(a) on Patent Application No. 2017-194506 filed in Japan
on Oct. 4, 2017 and Patent Application No. 2018-113134 filed in
Japan on Jun. 13, 2018, the entire contents of which are hereby
incorporated by reference.
BACKGROUND
The present disclosure relates to a light beam direction control
element, a display device, and a manufacturing method for a light
beam direction control element.
Flat panel display devices are used as display devices of various
information processing devices such as mobile phones, PDAs
(personal digital assistants), ATMs (automatic teller machines, and
personal computers, and in recent years, flat panel display devices
with a wide viewing angle are being put into practical use.
An example of such a flat panel display device is a liquid crystal
display device, for example. A generally known configuration for a
liquid crystal display device is one in which the liquid crystal
display device has installed therein an optical element that
adjusts the output direction of light entering from the rear, a
backlight that emits uniform light towards the optical elements,
and a liquid crystal display that displays images.
Also, as liquid crystal display devices have increased in size and
are used in more applications, various light orientation
characteristics are required.
In particular, there are needs such as to restrict the viewing
angle to prevent others from viewing the screen in order to prevent
divulging of information, and preventing emission of light in
unneeded directions. As an optical element that can meet such
needs, an optical film that can restrict the viewing angle (or
light output range) of a display has been proposed and put into
practical use.
However, in a liquid crystal display device with such an optical
film, there is a need to remove the optical film every time the
display is to be viewed from multiple directions simultaneously.
This would require the user to engage in a complex and
time-consuming process, and thus, there is increased demand to be
able to easily switch between a wide viewing angle and a narrow
viewing angle without requiring the user to remove the optical
film.
Thus, a light beam direction control element that can switch the
display between a wide viewing angle mode and a narrow viewing
angle mode according to need is proposed. Examples of such a
technique pertaining to a light beam direction control element
include the specification of U.S. Pat. No. 7,751,667 (Patent
Document 1) and WO 2015/122083 (Patent Document 2).
FIG. 16 is a cross-sectional view of a light beam direction control
element disclosed in Patent Document 1. A light beam direction
control element 611 disclosed in Patent Document 1 has a
transparent substrate 621, a transparent conductive film 631
disposed on a main surface 621a of the transparent substrate 621, a
plurality of transparent pillars 640 that are formed so as to be
separated from each other on the main surface 631a of the
transparent conductive film 631, and a mixed body 660 that is a
mixture of a transparent solvent and a light-absorption element
disposed between the transparent pillars 640. Also, in the light
beam direction control element 611 disclosed in Patent Document 1,
a transparent cover 622 having a main surface 622a on which the
transparent conductive film 632 is provided, is disposed on top
surfaces 640a of the transparent pillars 640.
FIG. 17 is a cross-sectional view of a light beam direction control
element disclosed in Patent Document 2. A light beam direction
control element 711 disclosed in Patent Document 2 has a first
transparent substrate 721, a plurality of conductive
light-shielding film patterns 731 that are disposed so as to be
separated from each other on a main surface 721a of the first
transparent substrate, an electrophoretic element 760 disposed on a
main surface 731a of each conductive light-shielding film pattern
731, and light-transmissive regions 740 that are formed on the main
surface 721a of the first transparent substrate and between the
electrophoretic elements 760. Also, in the light beam direction
control element 711 disclosed in Patent Document 2, a second
transparent substrate 722 having a main surface 722a on which the
transparent conductive film 732 is provided, is disposed on top
surfaces 740a of the light-transmissive regions 740.
However, the light beam passing through the light beam direction
control element 161 disclosed in Patent Document 1 is reflected at
the interface between the transparent substrate 621 and the
transparent conductive film 631, at the interface between the
transparent conductive film 631 and the transparent pillars 640, at
the interface between the transparent pillars 640 and the
transparent conductive film 632, and at the interface between the
transparent conductive film 632 and the transparent cover 622,
which reduces transmittance.
Similarly, the light beam passing through the light beam direction
control element 711 disclosed in Patent Document 2 is reflected at
the interface between the light-transmissive regions 740 and the
transparent conductive film 732, and at the interface between the
transparent conductive film 732 and the second transparent
substrate 722, which reduces transmittance.
SUMMARY
An aspect of the present disclosure adopts the following
constitutions to solve the above problems. A light beam direction
control element includes: a first transparent substrate; a second
transparent substrate disposed so as to face the first transparent
substrate; a first conductive film pattern that has openings and
that is formed on a first surface of the first transparent
substrate opposing the second transparent substrate; a second
conductive film pattern that has openings and that is formed on a
second surface of the second transparent substrate opposing the
first transparent substrate; an electrophoretic element that is
sandwiched between the first conductive film pattern and the second
conductive film pattern, and that includes light-shielding
electrophoretic particles that have a surface charge and a
transparent dispersion medium; and a plurality of
light-transmissive regions that are disposed between the first
transparent substrate and the second transparent substrate, that
are sandwiched between at least a portion of the openings of the
first conductive film pattern and at least a portion of the
openings of the second conductive film pattern, that have a surface
parallel to the first conductive film pattern and the second
conductive film pattern, and that have side walls surrounded by the
electrophoretic element.
It is to be understood that both the foregoing general description
and the following detailed description are exemplary and
explanatory and are not restrictive of this disclosure.
BRIEF DESCRIPTIONS OF DRAWINGS
The present disclosure can be appreciated by the description which
follows in conjunction with the following figures, wherein:
FIG. 1 is a cross-sectional view illustrating an example of a light
beam direction control element in narrow viewing angle mode (narrow
viewing angle state) according to Embodiment 1;
FIG. 2 is a cross-sectional view illustrating an example of the
light beam direction control element in wide viewing angle mode
(wide viewing angle state) according to Embodiment 1;
FIG. 3 is a graph illustrating simulation results for frontal
transmittance for each wavelength in the light beam direction
control element of Embodiment 1 and a light beam direction control
element of a related art;
FIG. 4 is a plan view of an example of the light beam direction
control element according to Embodiment 1;
FIG. 5 is a plan view of an example of the light beam direction
control element according to Embodiment 1;
FIG. 6 is a plan view of an example of the light beam direction
control element according to Embodiment 1;
FIG. 7A is an explanatory diagram illustrating an example of a step
(a transparent conductive film pattern formation step) of a
manufacturing method for the light beam direction control element
according to Embodiment 1;
FIG. 7B is an explanatory diagram illustrating an example of a step
(photosensitive resin layering step) of the manufacturing method
for the light beam direction control element according to
Embodiment 1;
FIG. 7C is an explanatory diagram illustrating an example of steps
(an exposure light radiation step and a position control step) of
the manufacturing method for the light beam direction control
element according to Embodiment 1;
FIG. 7D is an explanatory diagram illustrating an example of a step
(a transmissive region formation step) of the manufacturing method
for the light beam direction control element according to
Embodiment 1;
FIG. 7E is an explanatory diagram illustrating an example of a step
(a transparent substrate placement step) of the manufacturing
method for the light beam direction control element according to
Embodiment 1;
FIG. 7F is an explanatory diagram illustrating an example of a step
(an electrophoretic element filling step) of the manufacturing
method for the light beam direction control element according to
Embodiment 1;
FIG. 8 is a cross-sectional view illustrating an example of a light
beam direction control element in narrow viewing angle mode (narrow
viewing angle state) according to Embodiment 2;
FIG. 9 is an explanatory diagram illustrating an example of a step
(an illumination formation step) of a manufacturing method for the
light beam direction control element according to Embodiment 2;
FIG. 10 is a cross-sectional view illustrating an example of a
light beam direction control element in narrow viewing angle mode
(narrow viewing angle state) according to Embodiment 3;
FIG. 11 is a cross-sectional view illustrating an example of a
light beam direction control element in narrow viewing angle mode
(narrow viewing angle state) according to Embodiment 3;
FIG. 12A is an explanatory diagram illustrating an example of a
step (a transparent conductive film pattern formation step) of a
manufacturing method for the light beam direction control element
according to Embodiment 3;
FIG. 12B is an explanatory diagram illustrating an example of a
step (an insulating film layering step) of the manufacturing method
for the light beam direction control element according to
Embodiment 3;
FIG. 12C is an explanatory diagram illustrating an example of a
step (a photosensitive resin layering step) of the manufacturing
method for the light beam direction control element according to
Embodiment 3;
FIG. 12D is an explanatory diagram illustrating an example of steps
(an exposure light radiation step and position control step) of the
manufacturing method for the light beam direction control element
according to Embodiment 3;
FIG. 12E is an explanatory diagram illustrating an example of a
step (a transmissive region formation step) of the manufacturing
method for the light beam direction control element according to
Embodiment 3;
FIG. 12F is an explanatory diagram illustrating an example of a
step (a transparent substrate placement step) of the manufacturing
method for the light beam direction control element according to
Embodiment 3;
FIG. 12G is an explanatory diagram illustrating an example of a
step (an electrophoretic element filling step) of the manufacturing
method for the light beam direction control element according to
Embodiment 3;
FIG. 13 is a cross-sectional view illustrating an example of a
light beam direction control element in narrow viewing angle mode
(narrow viewing angle state) according to Embodiment 4;
FIG. 14 is a cross-sectional view illustrating an example of a
light beam direction control element in narrow viewing angle mode
(narrow viewing angle state) according to Embodiment 4;
FIG. 15 is an explanatory diagram illustrating an example of a
display device including a light beam direction control element
according to Embodiment 5;
FIG. 16 is a cross-sectional view illustrating an example of a
light beam direction control element according to a related
art;
FIG. 17 is a cross-sectional view illustrating an example of a
light beam direction control element according to a related
art;
FIG. 18 is a cross-sectional view illustrating an example of a
light beam direction control element in narrow viewing angle mode
(narrow viewing angle state) according to Embodiment 6;
FIG. 19 is a cross-sectional view illustrating an example of a
light beam direction control element in narrow viewing angle mode
(narrow viewing angle state) according to Embodiment 6;
FIG. 20A is an explanatory diagram illustrating an example of a
step (a transparent conductive film pattern formation step) of a
manufacturing method for the light beam direction control element
according to Embodiment 6;
FIG. 20B is an explanatory diagram illustrating an example of a
step (an insulating film layering step) of the manufacturing method
for the light beam direction control element according to
Embodiment 6;
FIG. 20C is an explanatory diagram illustrating an example of a
step (an insulating film partial removal step) of the manufacturing
method for the light beam direction control element according to
Embodiment 6;
FIG. 20D is an explanatory diagram illustrating an example of a
step (a photosensitive resin layering step) of the manufacturing
method for the light beam direction control element according to
Embodiment 6;
FIG. 20E is an explanatory diagram illustrating an example of steps
(an exposure light radiation step and a position control step) of
the manufacturing method for the light beam direction control
element according to Embodiment 6;
FIG. 20F is an explanatory diagram illustrating an example of a
step (a transmissive region formation step) of the manufacturing
method for the light beam direction control element according to
Embodiment 6;
FIG. 20G is an explanatory diagram illustrating an example of a
step (a transparent substrate placement step) of the manufacturing
method for the light beam direction control element according to
Embodiment 6;
FIG. 20H is an explanatory diagram illustrating an example of a
step (an electrophoretic element filling step) of the manufacturing
method for the light beam direction control element according to
Embodiment 6.
DETAILED DESCRIPTION OF EMBODIMENTS
Embodiments will be explained below with reference to attached
drawings. The embodiments are merely examples for realizing the
present disclosure, and it should be noted that the embodiments do
not limit the technical scope of the present disclosure. The same
reference characters are assigned to common components in the
respective drawings. The shapes depicted in the drawings do not
necessarily correspond to the actual dimensions and ratios.
Embodiment 1
FIG. 1 is a cross-sectional view illustrating an example of a light
beam direction control element in narrow viewing angle mode (narrow
viewing angle state). FIG. 2 illustrates an example of a light beam
direction control element in wide viewing angle mode (wide viewing
angle state).
A light beam direction control element 11 includes a first
transparent substrate 21, a transparent conductive film pattern 31,
light-transmissive regions 40, an electrophoretic element 60, a
second transparent substrate 22, and a transparent conductive film
pattern 32. The transparent conductive film pattern 31 is formed on
a surface 21a (main surface) of the first transparent substrate 21.
The transparent conductive film pattern 32 is formed on a surface
22a (main surface) of the second transparent substrate 22. The
first transparent substrate 21 and the second transparent substrate
22 are arranged such that a main surface 31a of the transparent
conductive film pattern 31 and a main surface 32a of the
transparent conductive film pattern 32 oppose each other.
The electrophoretic element 60 is disposed so as to be sandwiched
between the main surface 31a of the transparent conductive film
pattern 31 and the main surface 32a of the transparent conductive
film pattern 32. The electrophoretic element 60 includes
electrophoretic particles 61 and a dispersion medium 62. In the
example of FIGS. 1 and 2, the entire top surface 60a of the
electrophoretic element 60 is in contact with the transparent
conductive film pattern 32, and the entire bottom surface 60b of
the electrophoretic element 60 is in contact with the transparent
conductive film pattern 31.
The cross-sections of the light-transmissive regions 40 and the
dispersion medium 62 are depicted without a hatching pattern for
ease of viewing. The light-transmissive regions 40 are included in
the gap between the first transparent substrate 21, the transparent
conductive film pattern 31, the second transparent substrate 22,
and the transparent conductive film pattern 32.
The narrow viewing angle mode illustrated in FIG. 1 is realized by
dispersing the electrophoretic particles 61 in the electrophoretic
element 60 throughout the dispersion medium 62 disposed in the gap
between each light-transmissive region 40. Thus, the widening of
the light beam passing from bottom to top in the drawing is
restricted by the electrophoretic element 60 between the first
transparent substrate 21 and the second transparent substrate 22.
As a result, comparison of the light beam prior to and after
passing through indicates that the viewing angle is narrowed, and
the narrow viewing angle mode is set. By contrast, the wide viewing
angle mode illustrated in FIG. 2 is realized by concentrating the
electrophoretic particles 61 near the transparent conductive film
pattern 31. The electrophoretic particles 61 are gathered close to
the transparent conductive film pattern 31 by setting the potential
of the transparent conductive film pattern 31 relative to the
transparent conductive film pattern 32 at the opposite polarity to
the surface charge of the electrophoretic particles 61. Thus, the
widening of the light beam passing from bottom to top in the
drawing is mostly unrestricted by the electrophoretic particles 61
between the first transparent substrate 21 and the second
transparent substrate 22. As a result, comparison of the light beam
prior to and after passing through indicates that the difference in
viewing angle is mostly eliminated, and the wide viewing angle mode
is set.
In other words, if the surface charge of the electrophoretic
particles 61 is negative (-), then the transparent conductive film
pattern 31 is set to be a positive pole. If the surface charge of
the electrophoretic particles 61 is positive (+), then the
transparent conductive film pattern 31 is set to be a negative
pole.
Below, a case will be described of a configuration in which the
surface charge of the electrophoretic particles 61 is negative (-).
Even if the surface charge of the electrophoretic particles 61 is
positive (+), a similar configuration can be achieved by setting
the polarity of the transparent conductive film pattern 31 to the
opposite polarity.
The transparent conductive films 631 in FIG. 16 are disposed so as
to cover the main surface 621a of the transparent substrate 621,
but in the example of FIG. 1, the transparent conductive film
pattern 31 and the transparent conductive film pattern 32 are
formed so as to have openings, and the light-transmissive regions
40 are disposed in the openings. Particularly in the example of
FIG. 1, the light-transmissive regions 40 are not in contact with
the main surface 31a of the transparent conductive film pattern 31
or the main surface 32a of the transparent conductive film pattern
32.
Thus, it is possible to increase the proportion of light beams,
among the light beams entering the light-transmissive regions 40,
that have not passed interfaces with a high reflectance (interface
between the light-transmissive regions and the transparent
conductive films, and interface between the transparent conductive
films and the transparent substrate). As a result, it is possible
to realize a high transmittance light beam direction control
element 11.
FIG. 3 is a graph illustrating simulation results for frontal
transmittance for each wavelength in the light beam direction
control element 11 of the present embodiment and the light beam
direction control element 711 disclosed in Patent Document 2, which
is a related art document. Here, "frontal" indicates a perspective
from the direction normal to the surface of the substrate. FIG. 3
illustrates a transmittance 301 of the light beam direction control
element 11 of the present embodiment and a transmittance 302 of the
light beam direction control element 711 of FIG. 17. The simulation
results of FIG. 3 indicate that in all wavelengths, the
transmittance of the light beam direction control element 11 is 3
to 8% higher than that of the light beam direction control element
711.
Next, the configuration of the light beam direction control element
11 will be described in more detail with reference to FIG. 1. The
first transparent substrate 21 is made of a glass substrate,
polyethylene terephthalate (PET), polycarbonate (PC), polyethylene
naphthalate (PEN), or a cyclo-olefin polymer (COP), for example.
This similarly applies to the second transparent substrate 22.
A suitable thickness for the transparent conductive film pattern 31
is 10 nm to 1000 nm, and in the present embodiment, the thickness
is 50 nm. ITO (indium tin oxide), ZnO, IGZO (indium gallium zinc
oxide), or the like can be used to form the transparent conductive
film pattern 31, and ITO is used in the present embodiment. This
similarly applies to the transparent conductive film pattern
32.
In positions of the first transparent substrate 21 complementary to
the transparent conductive film pattern 31, the light-transmissive
regions 40 are formed. "Complementary positions" indicate a
positional relationship in which the transparent conductive film
pattern 31 and the light-transmissive regions 40 are alternately
disposed on the main surface of the first transparent substrate 21,
and it is preferable that the transparent conductive film pattern
31 and the light-transmissive regions 40 not overlap. This
similarly applies to the positional relationship between the
transparent conductive film pattern 32 on the second transparent
substrate 22 and the light-transmissive regions 40.
A suitable height for the light-transmissive regions 40 is 3 .mu.m
to 300 .mu.m, and in the present embodiment, the height is 60
.mu.m. Also, a suitable width for the light-transmissive regions 40
(light transmission pattern width) is 1 .mu.m to 150 .mu.m, and in
the present embodiment, the width is 20 .mu.m. Furthermore, a
suitable gap between the light-transmissive regions 40 is 0.25
.mu.m to 40 .mu.m, and in the present embodiment, the gap is 5
.mu.m.
Between the light-transmissive regions 40, the electrophoretic
element 60, which is a mixture of the electrophoretic particles 61
and the dispersion medium 62, is disposed, as described above.
Next, three examples of an arrangement of the light-transmissive
regions 40 and the electrophoretic element 60 are described with
reference to FIGS. 4 to 6. FIGS. 4 to 6 illustrate plan view
examples of the light beam direction control element 11. In FIGS. 4
to 6, the transparent conductive film pattern 32 and the second
transparent substrate 22 are not illustrated.
The example of FIG. 4 with a square pattern structure (first
example) has a plan view form in which square light-transmissive
regions 40 are arranged in a grid pattern, and the electrophoretic
element 60 (transparent conductive film patterns 31 and 32) forms a
square grid pattern that embeds the gaps between the plurality of
light-transmissive regions 40. In other words, the light beam
direction control element 11 in this case is formed such that a
light transmission pattern width 41a and the light transmission
pattern width 42a corresponding to the widths of the
light-transmissive regions 40 are equal to each other, and is also
formed such that a light-shielding film pattern width 41b and a
light-shielding film pattern width 42b corresponding to the widths
of the electrophoretic element 60 (gap between the
light-transmissive regions 40) are equal to each other.
In the example of FIG. 5 with a rectangular pattern structure
(second example), the plan view form of the light-transmissive
regions 40 and the electrophoretic element 60 (transparent
conductive film patterns 31 and 32) is that of a rectangular grid
pattern. In other words, the light beam direction control element
11 in this case is formed such that the light transmission pattern
width 42a is longer than the light transmission pattern width 41a.
On the other hand, the light-shielding film pattern width 41b and
the light-shielding film pattern width 42b are formed to be equal
in length.
In the example of FIG. 6 with a stripe pattern structure (third
example), the light-transmissive regions 40 and the electrophoretic
elements 60 (transparent conductive film patterns 31 and 32) form
stripes in a plan view. In other words, the light beam direction
control element 11 in this case is formed such that the light
transmission pattern width 41a of each light-transmissive region 40
and the light-shielding film pattern width 41b of the
electrophoretic elements 60 are formed alternately and
continuously. In the case of a stripe pattern, a plurality of the
transparent conductive film patterns 31 and 32 are electrically
connected at an external portion (not illustrated) and driven.
Below, an example of steps of a manufacturing method for the light
beam direction control element 11 of the present embodiment will be
described with reference to FIGS. 7A to 7F. First, as illustrated
in FIG. 7A, the transparent conductive film pattern 31 is formed on
the surface (main surface) of the first transparent substrate 21
(transparent conductive film pattern formation step). Next, as
illustrated in FIG. 7B, a transparent photosensitive resin layer 41
is layered as a negative photoresist film on the main surface side
of the first transparent substrate 21 on which the transparent
conductive film pattern 31 is formed (photosensitive resin layering
step). The transparent photosensitive resin layer 41 is a member to
become the light-transmissive regions 40 after the transmissive
region formation step to be described later.
Next, as illustrated in FIG. 7C, exposure light 75 is radiated onto
the transparent photosensitive resin layer 41 through a photomask
70 including a mask pattern 71, thereby exposing the transparent
photosensitive resin layer 41 (exposure light radiation step). When
performing the exposure light radiation step, alignment marks (not
illustrated) formed in the first transparent substrate 21 and the
photomask 70 are used such that the position of the mask pattern 71
overlaps the transparent conductive film pattern 31 to perform
control in which the positions of the photomask 70 and the first
transparent substrate 21 are adjusted (position control step).
Next, by performing a developing process on the exposed transparent
photosensitive resin layer 41, the plurality of light-transmissive
regions 40 that are separated from each other as illustrated in
FIG. 7D are formed (transmissive region formation step).
Next, using alignment marks (not illustrated) formed on the second
transparent substrate 22 and the first transparent substrate 21,
the second transparent substrate 22 provided with the transparent
conductive film pattern 32 is placed on the surfaces of the
light-transmissive regions 40 as illustrated in FIG. 7E
(transparent substrate placement step).
Then, as illustrated in FIG. 7F, the gaps formed between the
transparent conductive film pattern 31, the light-transmissive
regions 40, and the transparent conductive film pattern 32 are
filled with the electrophoretic element 60 (electrophoretic element
filling step).
In the description based on FIGS. 7A to 7F, a method was described
in which the phoretic element filling step is performed after the
transparent substrate placement step, but the light beam direction
control element 11 could be manufactured in a similar manner even
if the order of these two steps were reversed.
In other words, after performing steps similar to what was
described with reference to FIGS. 7A to 7D, a process may be
performed in which the phoretic element filling step in which the
electrophoretic element 60 fills the gaps between the
light-transmissive regions 40 is performed before the transparent
substrate placement step, and then, the transparent substrate
placement step is performed in which the second transparent
substrate 22 including the transparent conductive film pattern 32
is placed on the surfaces of the light-transmissive regions 40 and
the electrophoretic element 60.
Here, the exposure light 75 used for exposure is parallel light,
that is parallel to the layering direction (direction in which the
transparent photosensitive resin layer 41 and the like are
layered). A UV light source is used as the light source for the
exposure light 75, and in the exposure light radiation step of the
present embodiment, UV light with a wavelength of 365 nm is
radiated as the exposure light 75, for example.
A suitable amount of exposure during radiation is ranging from 100
mJ/cm.sup.2 to 1000 mJ/cm.sup.2, and in the present embodiment, the
amount of exposure by the exposure light 75 is 200 mJ/cm.sup.2.
As a method for forming the transparent photosensitive resin layer
41 in the exposure light radiation step, a film deposition method
employing a slit die coater, a wire coater, an applicator, dry film
transfer, spray coating, screen printing, or the like can be used,
for example. By such a film deposition method, in the present
embodiment, the transparent photosensitive resin layer 41, an
appropriate thickness of which is 30 .mu.m to 300 .mu.m, is formed
to a thickness of 60 .mu.m.
Also, the chemically amplified photoresist (product name "SU-8")
made by MicroChem can be used for the transparent photosensitive
resin used in the transparent photosensitive resin layer 41, for
example. Characteristics of the transparent photosensitive resin
are as follows.
The first characteristic is that the resin is an epoxy
(specifically, a glycidyl ether derivative of a bisphenol A
novolac) negative resist in which, by radiating ultraviolet light
thereon, a photoinitiator generates an acid, and with this proton
acid as a catalyst, a curable monomer is polymerized. The second
characteristic is that in the visible light region, the resin has a
very high transparency.
The third characteristic is that the curable monomer contained in
the transparent photosensitive resin has a lower molecular weight
prior to curing, and thus, is highly soluble in a solvent such as
cyclopentanone, propylene glycol methyl ether acetate (PGMEA),
gamma-butyrolactone (GBL), or isobutyl ketone (MIBK); therefore,
the resin can easily be formed as a thick film.
The fourth characteristic is that the resin has a very high degree
of transparency in the near-ultraviolet wavelength range as well,
and thus, even if the film is formed to be thick, it allows through
ultraviolet light. The fifth characteristic is that, as a result of
having the above-mentioned characteristics, the resin can be formed
in a pattern with a high aspect ratio of 3 or greater. The sixth
characteristic is that there are many functional groups of curable
monomers, and thus, after curing, the monomer forms a very high
density crosslink, which provides very high thermal and chemical
stability. Thus, processing thereof after patterning is easy.
Although the aforementioned chemically amplified photoresist
(product name "SU-8") was used as the transparent photosensitive
resin layer 41, the transparent photosensitive resin layer is not
limited thereto, and any photocurable material may be used as long
as similar properties can be attained.
In the transmissive region formation step of FIG. 7D, after
exposure, a developing process is performed on the transparent
photosensitive resin layer 41. In other words, by developing the
transparent photosensitive resin layer 41 and then performing
thermal annealing (thermal annealing process) at 120 to 150.degree.
C. for 30 to 60 minutes, the transparent photosensitive resin layer
41 is divided into the plurality of light-transmissive regions 40.
If the first transparent substrate 21 is a glass substrate, for
example, then it is preferable that the above conditions be
150.degree. C. and 30 minutes.
The space width (light-shielding film pattern width) between the
light-transmissive regions 40 formed here is, as described above, 5
.mu.m. Also, if the light-transmissive regions 40 are made of SU-8,
the refractive index thereof is 1.5 to 1.6.
During the transparent substrate placement step of FIG. 7F, the
second transparent substrate 22 including the transparent
conductive film pattern 32 is disposed on the light-transmissive
regions 40. The second transparent substrate 22 is fixed to the
outer periphery of the first transparent substrate 21 through an
adhesive (not illustrated). The adhesive used for fixing the
substrate to each other may be thermosetting or UV-curable.
As described above, in the light beam direction control element 11
of the present embodiment, the transparent conductive film pattern
31 and the transparent conductive film pattern 32 are formed so as
not to be continuous but to have openings, and the openings are in
contact with the light-transmissive regions 40. Particularly in the
example of FIG. 1, the light-transmissive regions 40 are only in
contact with the openings, and not in contact with the main surface
31a of the transparent conductive film pattern 31 or the main
surface 32a of the transparent conductive film pattern 32.
Thus, it is possible to increase the proportion of light beams,
among the light beams entering the light-transmissive regions 40,
that have not passed interfaces with a high reflectance (interface
between the light-transmissive regions and the transparent
conductive films, and interface between the transparent conductive
films and the transparent substrate), and therefore, a high
transmittance light beam direction control element 11 can be
achieved.
Embodiment 2
Below, a light beam direction control element 11 of the present
embodiment will be described. Differences from Embodiment 1 will be
described. FIG. 8 is a cross-sectional view illustrating an example
of a light beam direction control element in narrow viewing angle
mode (narrow viewing angle state). In the light beam direction
control element 11 of Embodiment 2, the surface 21a (main surface)
of the first transparent substrate 21 has formed thereon not the
transparent conductive film pattern 31 but a conductive
light-shielding film pattern 30.
A suitable material for the conductive light-shielding film pattern
is a light-shielding conductive material such as aluminum,
chromium, copper, or chromium oxide, and in the present embodiment,
aluminum is used. A suitable thickness for the conductive
light-shielding film pattern 30 is ranging from 10 nm to 1000 nm,
and in the present embodiment, the thickness is 300 nm.
In the manufacturing method illustrated in FIGS. 7A to 7F, by using
the conductive light-shielding film pattern 30 instead of the
transparent conductive film pattern 31, it is possible to
manufacturing the light beam direction control element 11 of the
present embodiment. Below, another example of the manufacturing
method for the light beam direction control element 11 of the
present embodiment will be described.
FIG. 9 is a descriptive drawing illustrating an example of an
illumination formation step in the manufacturing process for the
light beam direction control element 11. In the manufacturing
process for the light beam direction control element 11 of the
present embodiment, the illumination formation step illustrated in
FIG. 9 may be employed instead of the exposure light radiation step
and the transmissive region formation step of the manufacturing
process of Embodiment 1. In the exposure light radiation step, the
exposure light 75 is radiated from the rear surface side of the
first transparent substrate 21 with the conductive light-shielding
film pattern 30 as a photomask, thereby patterning the transparent
photosensitive resin layer 41 (illumination formation step).
Parallel light is used as the exposure light 75 used for exposure,
and a UV light source is used as the light source. In the present
embodiment, UV light with a wavelength of 365 nm is used as the
exposure light 75. Regarding the amount of exposure, for which a
range of 100 mJ/cm.sup.2 to 1000 mJ/cm.sup.2 is suitable, 200
mJ/cm.sup.2 was set in this case as well.
In this manner, by using the conductive light-shielding film
pattern 30 as a photomask, in addition to the effects attained in
Embodiment 1, it is possible to attain a configuration whereby the
relative positions of the light-transmissive regions 40 and the
conductive light-shielding film pattern 30 are naturally
complementary, even without performing the position control step of
Embodiment 1 for adjusting the positions of the photomask 70 and
the first transparent substrate 21. Furthermore, it is possible to
manufacture the light beam direction control element 11 such that
the top surface 60a of the electrophoretic element 60 is in contact
with the transparent conductive film pattern 32, which is an
electrode, and the entire bottom surface 60b of the electrophoretic
element 60 is in contact with the conductive light-shielding film
pattern 30, which is an electrode, without performing the position
control step.
Embodiment 3
Below, a light beam direction control element 11 of the present
embodiment will be described. Differences from Embodiment 1 will be
described. FIGS. 10 and 11 are cross-sectional views illustrating
an example of the light beam direction control element 11 in narrow
viewing angle mode (narrow viewing angle state).
The light beam direction control element 11 of FIG. 10 further
includes an insulating film 81 and an insulating film 82. The
insulating film 81 is formed in a layer on the surface 21a (main
surface) of the first transparent substrate 21 so as to cover the
transparent conductive film pattern 31. The insulating film 82 is
formed in a layer on the surface 22a (main surface) of the second
transparent substrate 22 so as to cover the transparent conductive
film pattern 32. The light-transmissive regions 40 and the
electrophoretic element 60 are interposed between the insulating
film 81 and the insulating film 82. Examples of a material to form
the insulating film 81 and the insulating film 82 include silicon
oxide, silicon nitride, or the like.
In the light beam direction control element 11 of FIG. 11, the
conductive light-shielding film pattern 30 is formed instead of the
transparent conductive film pattern 31 in FIG. 10. Details of the
conductive light-shielding film pattern 30 are as described in
Embodiment 2.
An example of a manufacturing method for the light beam direction
control element of FIG. 10 will be described with reference to
FIGS. 12A to 12G. The transparent conductive film pattern formation
step of FIG. 12A is similar to the transparent conductive film
pattern formation step of FIG. 7A, and thus, descriptions thereof
are omitted. In FIG. 12B, the insulating film 81 is formed on the
first transparent substrate 21 on which the transparent conductive
film pattern 31 is formed by a method such as CVD (chemical vapor
deposition) so as to cover the transparent conductive film pattern
31 (insulating film layering step).
Next, as illustrated in FIG. 12C, in a manner similar to FIG. 7B, a
transparent photosensitive resin layer 41 is layered as a negative
photoresist film on the main surface side of the first transparent
substrate 21 on which the transparent conductive film pattern 31
and the insulating film 81 are formed (photosensitive resin
layering step).
Next, as illustrated in FIG. 12D, in a manner similar to FIG. 7C,
exposure light 75 is radiated onto the transparent photosensitive
resin layer 41 through a photomask 70 including a mask pattern 71,
thereby exposing the transparent photosensitive resin layer 41
(exposure light radiation step). When performing the exposure light
radiation step, the positions of the photomask 70 and the first
transparent substrate 21 are adjusted such that the position of the
mask pattern 71 overlaps the transparent conductive film pattern 31
(position control step).
Next, as illustrated in FIG. 12E, in a manner similar to FIG. 7D,
by performing a developing process on the exposed transparent
photosensitive resin layer 41, the plurality of light-transmissive
regions 40 that are separated from each other as illustrated in
FIG. 7D are formed (transmissive region formation step).
Next, as illustrated in FIG. 12F, the second transparent substrate
22 including the transparent conductive film pattern 32 and the
insulating film 82 is disposed on the surfaces of the
light-transmissive regions 40 (transparent substrate placement
step). Then, as illustrated in FIG. 12G, the gaps formed between
the transparent conductive film pattern 31, the light-transmissive
regions 40, and the transparent conductive film pattern 32 are
filled with the electrophoretic element 60 (phoretic element
filling step).
The manufacturing method for the light beam direction control
element 11 of FIG. 11 is similar to the manufacturing method for
the light beam direction control element 11 of FIG. 10, but the
illumination formation step (rear surface exposure) described with
reference to FIG. 8 in Embodiment 2 may be employed instead of the
exposure light radiation step and the transmissive region formation
step.
In the light beam direction control element 11 of the present
embodiment, as a result of insulating films being disposed on the
surfaces of the transparent conductive films (or conductive
light-shielding film pattern), which are electrodes, insulation
between the electrodes is improved. Also, it is possible to
mitigate adhesion of the electrophoretic particles 61 onto the
surfaces of the electrodes. Thus, it is possible to mitigate
deterioration of the electrophoretic element 60 resulting from
adhesion of the electrophoretic particles 61 onto the surfaces of
the electrodes. Also, it is possible to apply a stronger electric
field and improve responsiveness.
Embodiment 4
Below, a light beam direction control element 11 of the present
embodiment will be described. Differences from Embodiment 1 will be
described. FIG. 13 is a cross-sectional view illustrating an
example of a light beam direction control element 11 in narrow
viewing angle mode (narrow viewing angle state). In the light beam
direction control element 11 of FIG. 13, a pattern width A of the
transparent conductive film pattern 31 and the transparent
conductive film pattern 32 is greater than a width B of the
electrophoretic element 60.
Specifically, in the present embodiment in which the width of the
light-transmissive regions 40 is 20 .mu.m and the width B of the
electrophoretic element 60 between the light-transmissive regions
40 is 5 .mu.m, the pattern width A of the transparent conductive
film pattern 31 and the transparent conductive film pattern 32 is
greater than 5 .mu.m and less than 25 .mu.m, and 6 .mu.m is a
suitable width therefor, for example. Also, projection widths C and
D of the transparent conductive film pattern 31 and the transparent
conductive film pattern 32 from the electrophoretic element 60 are
both greater than 0 .mu.m and less than 20 .mu.m, and 1 .mu.m is a
suitable width therefor, for example.
The manufacturing method for the light beam direction control
element 11 of FIG. 13 is similar to the manufacturing method of
Embodiment 1, for example. In the light beam direction control
element 11 of FIG. 13, as a result of the pattern width A being
greater than the width B of the electrophoretic element 60, it is
possible to manufacture the light beam direction control element 11
such that the top surface 60a of the electrophoretic element 60 is
in contact with the transparent conductive film pattern 32, which
is an electrode, and the entire bottom surface 60b of the
electrophoretic element 60 is in contact with the transparent
conductive film pattern 31, which is an electrode, even if some
positional offset were to occur in the position control step.
FIG. 14 is a cross-sectional view illustrating an example of a
light beam direction control element 11 in narrow viewing angle
mode (narrow viewing angle state). The light beam direction control
element 11 of FIG. 14 differs from the light beam direction control
element 11 of FIG. 19 in that a width A' of the transparent
conductive film pattern 31 is greater than the pattern width A of
the transparent conductive film pattern 32.
Specifically, if the pattern width A of the transparent conductive
film pattern 32 is 5 .mu.m, for example, then 6 .mu.m to 10 .mu.m
would be suitable for the pattern width A' of the transparent
conductive film pattern 31. The manufacturing method for the light
beam direction control element 11 of FIG. 14 is similar to the
manufacturing method of Embodiment 1, for example.
In the light beam direction control element 11 of FIG. 14, as a
result of the fact that the pattern width A' of the transparent
conductive film pattern 31 is greater than the pattern width A of
the transparent conductive film pattern 32, it is possible to allow
for some positional offset in not only the position control step
but also the transparent substrate placement step. Thus, it is
possible to manufacture the light beam direction control element 11
such that the top surface 60a of the electrophoretic element 60 is
in contact with the transparent conductive film pattern 32, which
is an electrode, and the entire bottom surface 60b of the
electrophoretic element 60 is in contact with the transparent
conductive film pattern 31, which is an electrode, even if some
positional offset were to occur in the transparent substrate
placement step.
Embodiment 5
Below, in the present embodiment, an example of a display device
including a light beam direction control element 11 will be
described with reference to FIG. 15. The display device includes
the light beam direction control element 11 and a display unit 100
that displays images, which are bonded together by a transparent
adhesive layer, for example. In the example of FIG. 15, the light
beam direction control element 11 is disposed on the surface 100a
(display surface) side of the display unit 100. In other words, the
surface opposite the main surface of the second transparent
substrate 22 is bonded to the display unit 100. The light beam
direction control element 11 in the example illustrated in FIG. 15
is the light beam direction control element 11 of FIG. 11 in which
the conductive light-shielding film pattern 30 is formed on the
first transparent substrate 21 (may alternatively be the light beam
direction control element 11 of FIG. 8, for example).
In the example of FIG. 15, the light beam direction control element
11 is disposed such that the conductive light-shielding film
pattern 30 is on the viewer side, or in other words, such that the
transparent conductive film pattern 32 is closer to the surface
100a of the display unit 100. By arranging the light beam direction
control element 11 in this manner, even if an optical moire pattern
were to occur as a result of an offset in the relative positions of
the transparent conductive film pattern 32 and the
light-transmissive regions 40, the optical moire would not be
visible by the viewer, and an excellent display state can be
maintained.
Embodiment 6
Below, a light beam direction control element 11 of the present
embodiment will be described. Differences from Embodiment 3 will be
described. FIGS. 18 and 19 are cross-sectional views illustrating
an example of the light beam direction control element 11 in narrow
viewing angle mode (narrow viewing angle state).
The light beam direction control element 11 of FIG. 18 includes an
insulating film pattern 111 and an insulating film pattern 112. The
insulating film pattern 111 is formed in a pattern on a surface 21a
(main surface) of the first transparent substrate 21. The elements
(excluding the openings) of the insulating film pattern 111 cover
the elements (excluding the openings) of the transparent conductive
film pattern 31. Also, the insulating film pattern 112 is formed in
a pattern on a surface 22a (main surface) of the second transparent
substrate 22. The elements (excluding the openings) of the
insulating film pattern 112 cover the elements of the transparent
conductive film pattern 32. Elements of the insulating film pattern
111 that cover the plurality of elements (excluding the openings)
of the transparent conductive film pattern 31 may be provided.
The light-transmissive regions 40 and the electrophoretic element
60 are interposed between the surface 21a (main surface) of the
first transparent substrate 21, the insulating film pattern 111,
the surface 22a (main surface) of the second transparent substrate
22, and the insulating film pattern 112. Examples of a material to
form the insulating film pattern 111 and the insulating film
pattern 112 include silicon oxide, silicon nitride, or the
like.
In the light beam direction control element 11 of FIG. 19, the
conductive light-shielding film pattern 30 is formed instead of the
transparent conductive film pattern 31 in FIG. 18. Details of the
conductive light-shielding film pattern 30 are as described in
Embodiment 2.
An example of a manufacturing method for the light beam direction
control element of FIG. 18 will be described with reference to
FIGS. 20A to 20H. The transparent conductive film pattern formation
step of FIG. 20A and the insulating film formation step of FIG. 20B
are similar to the transparent conductive film pattern formation
step of FIG. 12A and the insulating film formation step of FIG.
12B, and thus, descriptions thereof are omitted. Next, in FIG. 20C,
portions of the insulating film 81 other than those that cover the
respective elements of the transparent conductive film pattern 31
are removed, thereby forming the insulating film pattern 111
(insulating film partial removal step).
Next, as illustrated in FIG. 20D, in a manner similar to FIG. 7B, a
transparent photosensitive resin layer 41 is layered as a negative
photoresist film on the main surface side of the first transparent
substrate 21 on which the transparent conductive film pattern 31
and the insulating film pattern 111 are formed (photosensitive
resin layering step).
Next, as illustrated in FIG. 20E, in a manner similar to FIG. 7C,
exposure light 75 is radiated onto the transparent photosensitive
resin layer 41 through a photomask 70 including a mask pattern 71,
thereby exposing the transparent photosensitive resin layer 41
(exposure light radiation step). When performing the exposure light
radiation step, the positions of the photomask 70 and the first
transparent substrate 21 are adjusted such that the position of the
mask pattern 71 overlaps the transparent conductive film pattern 31
(position control step).
Next, as illustrated in FIG. 20F, in a manner similar to FIG. 7D,
by performing a developing process on the exposed transparent
photosensitive resin layer 41, the plurality of light-transmissive
regions 40 that are separated from each other as illustrated in
FIG. 20F are formed (transmissive region formation step).
Next, as illustrated in FIG. 20G, the second transparent substrate
22 including the transparent conductive film pattern 32 and the
insulating film pattern 112 is disposed on the surfaces of the
light-transmissive regions 40 (transparent substrate placement
step). Then, as illustrated in FIG. 20H, the gaps formed between
the first transparent substrate 21, the insulating film pattern
111, the second transparent substrate 22, the insulating film
pattern 112, the transparent conductive film pattern 31, the
light-transmissive regions 40, and the transparent conductive film
pattern 32 are filled with the electrophoretic element 60
electrophoretic element filling step).
The manufacturing method for the light beam direction control
element 11 of FIG. 19 is similar to the manufacturing method for
the light beam direction control element 11 of FIG. 18, but the
illumination formation step (rear surface exposure) described with
reference to FIG. 8 in Embodiment 2 may be employed instead of the
exposure light radiation step and the transmissive region formation
step.
In the light beam direction control element 11 of the present
embodiment, as a result of patterning the insulating films disposed
on the surfaces of the transparent conductive films (or conductive
light-shielding film pattern), which are electrodes, a light beam
direction control element 11 with an even higher transmittance can
be achieved.
Details of the embodiments were described above with reference to
the drawings, but the specific configuration of the present
disclosure is not limited thereto, and various modifications and
equivalent configurations are included within the spirit of the
included claims.
* * * * *